Hemisphere:  Southern  ·  Constellation: Canis Major (CMa)  ·  Contains:  16 omi01 CMa  ·  The star ο1CMa
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            Gary Imm
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            Gary Imm
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Imaging telescopes or lenses: Takahashi TOA-130NFB

Imaging cameras: ZWO ASI 6200 MM Pro

Mounts: Astro-Physics Mach1GTO

Guiding cameras: ZWO ASI 174 MM Mini

Software: Main Sequence Software Sequence Generator Pro  ·  Pixinsight  ·  Stark Labs PHD2 2.6.3

Filters: Chroma OIII 3nm  ·  Chroma Red 2" unmounted  ·  Chroma Ha 3nm  ·  Chroma Blue 2" unmounted  ·  Chroma Green 2" unmounted

Accessory: ZWO M68 OAG  ·  ZWO EFW 2″X7  ·  Takahashi Flattener TOA-67  ·  Feathertouch Focuser Boss II Electronic Focusing Control

Dates:Feb. 19, 2021Feb. 21, 2021Feb. 22, 2021

Chroma Blue 2" unmounted: 30x120" (1h) (gain: 0.00) -20C bin 1x1
Chroma Green 2" unmounted: 30x120" (1h) (gain: 0.00) -20C bin 1x1
Chroma Ha 3nm: 36x300" (3h) (gain: 100.00) -20C bin 1x1
Chroma OIII 3nm: 36x300" (3h) (gain: 100.00) -20C bin 1x1
Chroma Red 2" unmounted: 30x120" (1h) (gain: 0.00) -20C bin 1x1

Integration: 9h

Avg. Moon age: 8.64 days

Avg. Moon phase: 62.86%

Astrometry.net job: 4241578

RA center: 6h 54' 22"

DEC center: -23° 55' 43"

Pixel scale: 1.549 arcsec/pixel

Orientation: 1.925 degrees

Field radius: 1.136 degrees

Resolution: 4408x2906

Locations: Backyard (Mag 20.8 - Bortle 4.5), Onalaska, Texas, United States

Data source: Backyard


This object is a Wolf-Rayet emission nebula located 3000 light years away in the constellation of Canis Major at a declination of -24 degrees. Its nature is a bit different than the classic planetary nebula, though most people call it a planetary nebula anyway. The nebula spans 45 arc-minutes in our apparent view and is 40 light years in diameter.

The nebula is being blown out by fast winds from a hot huge 6.8 magnitude Wolf-Rayet star (HD 50896), the bright blue star near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of our Sun and are thought to be in a brief, pre-supernova phase. The gas in this nebula is primarily oxygen gas, which not only forms the object but permeates the background sky of the image.

Although the nebula is roughly spherical, it is elongated along an axis that runs from bottom left to top right of the image. This is likely due to bi-polar gas expulsion from the opposite stellar poles.

My favorite part of this object, aside from the overall shape, is how the oxygen nebula is slightly larger in diameter than the hydrogen nebula. This is seen in the image where the white nebula surfaces at top and bottom right sit slightly inside the cyan oxygen surface.

The bright 3.9 magnitude red supergiant star is Omicron Canis Majoris (HD 50877). The distance estimates to it are uncertain, so it is not clear whether this star is in front of or behind the nebula. This cool (4000 K) star is about 8 times as massive as our Sun, 280 times its diameter, and shines with 16,000 times its luminosity.